Like Gao Min Wang Xiaoyang Sean Wang Sriram Padmanabhan A learning-based approach to estimate statistics of operators in continuous queries: a case study. 66-72 2003 conf/dmkd/2003 DMKD http://doi.acm.org/10.1145/882082.882097 db/conf/dmkd/dmkd2003.html#GaoWWP03